SYNOPSIS
  void log_file(string file, string message)

DESCRIPTION
  Append a message to a log file. All log files are in the
  directory /log. '/log/' is automatically prepended to
  the file name.
  If the file grows larger than 50 KByte, it is renamed to
  /log/<file>.old, and a new log file is started.
  This way the amount of logfiles is kept in limits.

EXAMPLE
  log_file("foobar.err", "something went wrong\n");

SEE ALSO
  write_file(E)
